noun, na-adjective, noun which may take the genitive case particle 'no'
shamelessness; brazenness; impudence; nerve
Describes a person who is utterly unashamed, thick-skinned, or brazen in the face of criticism. Often used in set phrases like 鉄面皮な態度 or 鉄面皮にもほどがある.
彼の鉄面皮な態度にはあきれてしまった。
I was appalled by his shameless attitude.
あんな失敗をしておいて平然と
To act so nonchalant after such a failure—there's a limit to how brazen you can be.
Similar to 厚かましい, but often implies a more persistent, pushy impudence. 鉄面皮 is more about a brazen lack of shame rather than pushiness.
Compound of 鉄 (iron) + 面皮 (face skin), literally 'iron face skin'. The exact origin is uncertain, but it is a vivid metaphor for a person so shameless that their face is like iron, impervious to shame.